DESCRIPTION: The overall objective of this research proposal is to study the role and regulation of the glutamine transporter system ASC in hepatocellular transformation. The proposal contains four specific hypotheses: 1) Accelerated rates of glutamine uptake via System ASC are a consistent feature of human hepatomas. 2) ASC mediated glutamine transport is necessary, but not alone sufficient for a tumorigenic phenotype. 3) Growth of human hepatomas is regulated by delivery of glutamine to the cytoplasm. 4) System ASC activity is regulated by cellular growth status. To test these four hypotheses, the investigators propose four specific aims: 1) They will examine glutamine transport in cells or plasma membrane vesicles from surgical biopsies that include hepatic tumor and normal surrounding parenchyma. 2) A nontumorigenic immortalized human liver epithelial cell line (THLE-5B) will be stably transfected with the hepatoma ASC gene and injected into nude mice for evaluation of tumorigenic potential. 3) Human hepatomas and immortalized human liver cells will be grown in the presence of physiologic glutamine levels and in the presence or absence of excess System ASC substrates and the effects on proliferation evaluated. 4) ASC mediated glutamine uptake will be evaluated at both the activity and molecular levels in synchronized hepatoma and THLE-5B cells after growth modulation by nutrient supply or biochemicals.